It is common practice to pass electrical conductors and cable through conduit (typically metal conduit) from one point to another as a means of providing support and protection for the conductors and cables.
The term "conduit" refers to pipe having dimensional and other characteristics suitable for use by the electrical industry as is well known to those ordinarily skilled in the art. Although hereinafter referred to as conduit, it is to be understood that the term "conduit" as used herein means metal conduit also includes metal pipe which is not conduit but able to serve the purpose of conduit where desired.
Conduit may often inadvertently or unavoidably provide a passage-way from a region in which explosive, corrosive, toxic or otherwise undesirable vapors are present to a region free of such vapors. In an effort to prevent the passage of such vapors through the conduit to the vapor-free region, it has been common practice in the past to pack the openings between the conduit and the conductors and cables with some type of heavy pliable material. In recognizing the problem, minimum performance criteria have been established under relevant sections of the National Electrical Code for controlling the manner in which conduit located in hazardous locations is sealed.
The manner in which conduit has been sealed in the past, however, has typically involved expensive fittings of complex design that are commonly adapted to be used in conjunction with sealant materials which may require mixing of several components to impart sufficient viscosity to withstand the pressure of the vapors and require costly inventory of multiple components.
One method commonly used for sealing electrical conductors at a junction between conduit are metal connectors sold by Crouse-Hinds Company under series numbers EYS, EZS, EYD, EZD and ECD. The connectors feature a port filling entrance into which a sealant, recommended and sold by Crouse-Hinds Company under the Trademark "Chico" can be poured to provide a barrier against the flow of vapor through the conduits. The connectors further feature the use of a fiber sold by Crouse-Hinds Company under the Trademark "Chico & Fiber" for providing a dam within the connector to prevent the flow of the sealing compound into the conduits.
Another method of connecting tubing together is by the use of couplings made from a heat recoverable metal such as described in U.S. Pat. Nos. 4,035,007 and 4,135,743, the disclosures of which are incorporated herein by reference. Couplings of this type are made from special alloys such as nickel and Titanium alloys which if expanded in the martensitic state will contract radially inwardly when heated from the martensitic to the austenitic state. As used herein the term "heat recoverable metal" (or metallic material) means metallic materials including the materials disclosed in the above reference patents and other alloys such as alloys of copper, zinc and aluminum which, when shaped into the form of a coupling, are able to shrink and contract tightly about the end of metal tubing in response to a suitable amount of heat and firmly grip the tubing over its normal temperature usage range.
Although couplings in the form of a sleeve made from a heat recoverable metallic material may be used to advantage in connecting a junction between metal conduits, they would not by themselves provide a solution to providing individual protection to one or more electrical conductors contained within the space between the conduits nor would they prevent dangerous or otherwise undesirable vapor from using the conduit as a passageway from one location to another.
In view of the need to provide a simple and low cost method of connecting metal conduit to individually protect one or more electrical conductors extending through a connector between the conduits in addition to providing a barrier against the flow of vapor through the conduits represents a problem which, although long known to industry, has not, up until the time of the present invention, had a completely satisfactory solution.